'felsic' originates from an early 20th-century geological coinage combining the older form 'felspar' (an alternative spelling of 'feldspar') with the adjectival suffix '-ic', created in parallel with the term 'mafic'.

'felspar' itself is an older variant of 'feldspar', which comes from German 'Feldspat' ('Feld' = field + 'Spat' = spar), and the modern term 'felsic' developed in geology to describe rock chemistry.

Initially tied to the idea of 'of or pertaining to feldspar,' the term evolved to mean more generally 'silica- and feldspar-rich igneous rocks or magmas' in petrology.