How did 'less than' semantically shift to mean 'if not'?
What semantic notions underlie less than and IF NOT? How did less than semantically shift to mean IF NOT in at least these 5 languages? Just edit this post if you pine to add other languages with this semantic shift.
mid-15c., earlier onlesse, from (not) on lesse (than) "(not) on a less compelling condition (than);" see less. The first syllable originally on, but the negative connotation and the lack of stress changed it to un-.
à moins que = sauf si.
a menos que means 'unless' in Spanish and Portuguese.
a meno che means 'unless' in Italian.
The etymology for 'unless' reveals the etymon of 'un' as 'on', which suggests 'un ← on' in English to mean the same as à and a in the 4 other Romance languages.
The above substantiates the same semantic shift in at least 4 languages,
from the prepositional phrase
- a/à/un ← on (preposition) +
- less (adverb) +
- than (comparative preposition).
Unless is a word formed from a prepositional phrase in Middle English
of|in|on lesse than...It refers to a sufficient condition. (The mnemonic: less <=> sufficiency).