An Etymological Dictionary of Astronomy and Astrophysics

A suffix forming agent nouns, occurring originally in loanwords from Anglo-French; it now functions in E. as an orthographic variant of -er.

Etymology (EN): From M.E., from O.Fr. -o(u)r, from L. or-, extracted from -tor; Gk. -tor (e.g. dotor “giver,” genetor “begetter,” ktistor “founder”); cf. Av. -tar- (dātar- “giver,” astar- “thrower,” baxtar- “tributor”); Skt. -tr- (kartr- “doer,” dhātr- “founder,” astr- “thrower”).

Etymology (PE): Agent suffix -gar, variant -gâr, -kâr,
from kar-, kardan “to do, to make” (Mid.Pers. kardan; O.Pers./Av. kar- “to do, make, build;” Av. kərənaoiti “makes;” cf. Skt. kr- “to do, to make;” krnoti “makes,” karma “act, deed;” PIE base k^wer- “to do, to make”).
Suffix -âr, as in parastâr, xaridâr, foruxtâr, virâstâr, xâstâr, nemudâr. Agent suffix -andé, used with verbs.