Etymology: < Anglo-Norman and Old French, Middle French as (French as ) side of a dice marked with a single spot (12th cent. in Old French; also in ambesas ames-ace n.), playing card marked with a single spot (although this is first attested slightly later: 1546) < classical Latin as coin, monetary unit, unit of weight, arithmetical unit (see as n.¹). The sense ‘side of a dice marked with a single spot’ probably either developed in Old French on account of the use of the Roman coin in stakes in games of chance, or reflects the sense ‘arithmetical unit’ (attested in Vitruvius and other authors) of classical Latin as. Compare Old Occitan as (12th cent.), Catalan as (15th cent.), Spanish as (13th cent.), Portuguese ás (13th cent.), Italian asso (14th cent.; probably < French). The Latin word was also borrowed into other Germanic languages at an early date; compare Middle Dutch aes (Dutch aas), Middle Low German es, Old High German (in late sources) essa, essi (Middle High German esse, German †Aß; German As (18th cent.) is a later reborrowing < French), and (probably via Middle Low German) Old Swedish as (Swedish äss), Danish es.With the uses to denote worthlessness or a negligible amount (see senses A. 1a, A. 2a) compare similar uses in French, attested from the 12th cent. onwards, e.g. ne valoir un as ‘not to be worth an ace’ (12th cent.), n'être pas si grand comme as en dé au regard de quelque chose ‘not to be as big as an ace on a die in comparison to something’, ne pas donner deux as de quelque chose ‘not to give two aces for something’ (both mid 14th cent. or earlier); some of these uses may later have been reapprehended as involving the French name of the Roman coin, as as n.¹, which is first attested considerably later (1548) than the figurative phrases (compare similar uses of classical Latin as as n.¹, e.g. Catullus 5. 2-3 rumoresque senum severiorum Omnes unius aestimemus assis ‘let us count all the rumours of stern old men as worth but a penny’). In sense A. 4a, which is not paralleled in French until later (1868 in a sports context, (1920 denoting any exceptional or highly skilled person), apparently an extended use of the specific sense ‘highest-scoring playing card’ of sense A. 3). In sense A. 4b after French as (1915 in this sense, originally with reference to a pilot who had shot down ten enemy aircraft; compare quot. 1916). With the use as adjective compare earlier aces adj. In many dialects the word developed a palatal on-glide (compare the β. forms at earth n.¹).

Etymology: Initialism < the initial letters of angiotensin converting enzyme (see angiotensin converting enzyme n. at angiotensin n. Compounds); in later use also reinterpreted as an acronym.

Etymology: Shortened < either asexual n. or asexual adj., with the spelling ace intended to indicate the pronunciation clearly, and probably also with punning allusion to ace n.¹ and ace adj.¹ Compare earlier homo n.², bi n.², etc.

Etymology: < ace n.¹