Meaning

adjective has a good chance of being the case or of coming about

adjective likely but not certain to be or become true or real

adjective expected to become or be; in prospect

originFrom Middle English likely, likly, lykly, likliche, from Old English ġelīclīċe (“equally”) and Old Norse líkliga, glíkliga (“likely”), both from Proto-Germanic *līkalīka, equivalent to like + -ly (adverbial suffix).

Etymology from Wiktionary, CC BY-SA 3.0