I have nothing against metrication. Although if you're going to do it then stop using all imperials measurements - the mile and the pint in particular srill seem to be the norm. And why not do the same for the clock, that will stop people speaking of distances in hours when everyone knows the only way to express distance in a time sense is using the speed of light in a vacuum as a base.
As an author the one former range of sizes I miss most is those once used for paper. Today we simply use 'A' and a number but examine the list below and discover the wonderful expressions once used and where they originated. Note in most cases this requires examining the origin of the word as used in other senses for these are simply late loan words
Antiquarian - a reference to one who studies or well-versed in antiques, this is ultimately from 'antique' - this can be traced to an original meaning of 'before appearance'.
Atlas - undoubtedly coming to refer to paper sizes as this was used for maps, it comes from the god of Greek mythology and used for the book of maps because an image of the god said to hold the world on his shoulders appeared on the Atlas, sive cosmographicae meditationes de fabrica mundi a book of maps published by Flemish geographer Gerhardus Mercator in 1585. The Greek name is said to mean, appropriately enough, 'the bearer (of the heavens) and from Proto-Indo-European tele 'to lift, support' and the prefix a 'not, without'.
Emperor - a loan word from the Latin imperiator.and also 'empire'. The prefix is the same as Latin in 'not' with par-a, a Proto-Indo-European word meaning 'bring forward, bring forth' and mainly used in a 'birthing' sense. What is being said here is the empire is 'not born' but has always been, perhaps not practically but in essence.
Crown - used in many senses, all derived from the original Latin sense of 'wreath'.
Demy - only seen in this spelling for paper, it is easier to understand as 'demi', itself the French for 'half but derived from the suffix dis 'the opposite' and a root me 'between'.
Elephant - clearly a reference to size, the name of the animal has an unknown etymology, one not of Indo-European origins and thus, with few written examples, will likely prove impossible to explain.
Folio - is as it very much appears, a Latin word which means 'leaf' and is derived from Proto-Indo-European bhol-yo with the same meaning.
Foolscap - only ever having heard this and never in writing, as a child I always thought tis was 'fullscap'. Delightful if fairly recent etymology, the 'foo's cap' was that worn by a jester and used from around 1700 for the paper as it was originally watermarked with this very image.
Grand eagle - two words to define here, both with Proto-Indo-European origins. 'Grand' comes a word specifically meaning 'adult male relative other than the father' while 'eagle' is simply 'a great bird'.
Imperial - shares its etymology with 'emperor' above.
Octavo - is the Latin word for 'in the eighth' as was a printer's word for sheets folded so as to make eight leaves. Clearly the origin is the same as the Greek word for 'eight' which is ostensibly the same as the Proto-Indo-European okto and simply means 'eight'.
Princess - the female version of 'prince', itself sharing a root with 'prime' in Proto-Indo-European capere 'to take' and ultimately kap 'to grasp'.
Royal Sixto - again two words to define. 'Royal' began as a Proto-Indo-European adjective reg meaning 'move in a straight line'; while is similar to 'octavo' above except this is based on six.
Sheet - shares an origin with the cloth variety, originall meaning 'shroud' in Germanic languages but came from the Proto-Indo-European root skeud 'to chase, throw'.
Sixmo - again similar to 'octavo' above but based on six.
Still in use, at least to some degree, are the names given to the range of paper types. Again these often have to be looked at as words used in other sense as they ostensibly loan words.
Bank - began as the rise of land where Proto-Indo-European meant 'shelf' in the topographical sense.
Bond - etymologically speaking this is a variant of 'band', itself a variant of 'bind' which is exactly what the Proto-Indo-European bhendh meant and is also clearly the origin of 'bend'.
Brief - as a noun predates the verb (17th and 19th centuries respectively). However the adjective is much earlier, seen in English since the 13th century and ultimately from Proto-Indo-European mregh-u 'short'.
Cartridge - is a corruption of 'cartouche', a scroll-like ornament or a paper cartridge, then borrowed for 'a full charge for a pistol'. It is the 'paper' sense which is important, for this shaes a root with 'card'and 'chart' in the Greek khartes referring to 'a layer of papyrus' and itself derived from the Proto-Indo-European kars 'to scrape' in showing how paper from papyrus was produced.
Carbon - ultimately from the same root as 'coal, charcoal' and the rest in Proto-Indo-European ker or 'fire'.
Copy - can be traced to Proto-Indo-European op meaning 'to work, produce in abundance'.
Duplicating - is from 'duplicate' seen as a noun and an adjective but began as a verb. The first part is related to 'duo' meaning 'two' while the suffix comes from the same root as 'ply' or 'fold'.
Typing - is clearly derived from 'type' and this can be traced back to Proto-Indo-European tup meaning 'to strike, beat, knock'.
Wall - as in 'wallpaper' and comes from Proto-Indo-European walso meaning 'post' and what one needs to build a wall.
News - one of my least favourite things, but it does come from 'new' which, ironically, is not a new word at all, indeed Proto-Indo-European newo meant the same thing and it has probably changed little for thousands of years.
Wrapping - clearly derived from 'wrap', this first used as a verb and traced to Proto-Indo-European wer meaning 'to turn, bend'.
Greaseproof - clearly a combination of two words where 'grease' began in the Latin group of languages meaning 'thick, solid, fat', and 'proof' from 'prove' and Proto-Indo-European pro-bhwo 'being in front'.
Silver - as mentioned in earlier posts looking at colours, metals and elements and simply means 'white, shining'.