Vire engines came originally from Finland. The word "Vire" in Finnish can be translated in several different ways. It can mean "a breeze", or it can mean "alert", but also (and especially) "condition", "state", "atmosphere", "tune" or "health". If something or somebody is "in vire" it means "fit for a fight", "ready to go", "in good condition", "virile" (of a person) or "tuned" (of a motor or a radio receiver). It's anybody's guess which was the original manufacturers' intention.
Maybe Valmet were being deliberately vague about the meaning, because they used a pun on the word in one of their marketing slogans for the early Vire BV series of engines:
which translates as
In case you hadn't already worked it out, "vene" means "boat".
We English speakers who make the word "Vire" rhyme with "fire" (as in fire-engine, fireman, etc.) have got it wrong. Several helpful Finns have explained to me about their language. In general, they don't have any "silent" letters, and they stress each syllable equally. So "Vire" should be pronounced "vi-re" - the "i" sounds as in the English word "ship" and the "e" sounds as in the English word "bed".