Exact historical dictionary sense
Likely in Webster's 1913 dictionary
The 1913 record labels likely as adjective. Its source-bounded etymology and selected historical definition appear below.
[That is, like-like. See Like, a.]
Cross-verified historical senseIn Webster's Revised Unabridged Dictionary (1913), "likely" is labeled adjective. Its etymology is recorded as: "[That is, like-like. See Like, a.]" The selected historical definition says: "Worthy of belief; probable; credible; as, a likely story."