Innumerable means too many to be counted. Not infinite — simply past the point of counting.
It goes before a plural noun, so innumerable occasions or innumerable small kindnesses, and it is a deliberate exaggeration. Countless does exactly the same job and is far commoner in speech, which leaves innumerable sounding formal and slightly literary. The word is built from numerable with in- in front, though numerable itself is almost never used on its own.
1adjectiveinnumerableToo many to be counted.
“He had told the story on innumerable occasions.”
Also accepted in games: countless
Proto-Indo-European
*nem-
Latin
innumerābilis
Middle English
innumerable
English, today
innumerable
From in- + numerable; from Middle English innumerable, from Latin innumerābilis, from in- + numerābilis.
Etymology from Wiktionary, CC BY-SA