Meaning

noun an occurrence that involves the production of a union

noun the state of being combined into one body

noun the merging of adjacent sounds or syllables or words

originFirst appears c. 1555, in a translation by Richard Eden. From Middle French fusion, from Latin fūsiōnem (the accusative of fūsiō), from fusus, past participle of fundō (“to pour; to melt”) (see also found). Doublet of foison.

Etymology from Wiktionary, CC BY-SA 3.0