Fusion
mid 16th century: from Latin fusio(n- ), from fundere ‘pour, melt’.
wiktionary
1555, from Middle French fusion, from Latin fūsiōnem (the accusative of fūsiō), from fusus, past participle of fundō(“I pour, I melt”) (see also found). Doublet of foison.
etymonline
fusion (n.)
1550s, "act of melting by heat," from French fusion or directly from Latin fusionem (nominative fusio) "an outpouring, effusion," noun of action from fusus, past participle of fundere "to pour, melt" (from nasalized form of PIE root *gheu- "to pour"). Meaning "union or blending of different things; state of being united or blended" is by 1776; used especially in 19c, of politics, in early 20c. of psychology, atoms, and jazz (in nuclear physics sense, first recorded 1947; in musical sense, by 1972).
