A primitive root; to shine, i.e. (by analogy) be (causatively, make) oily or gross -- become (make, wax) fat.
H8080. shamen
I. [שָׁמֵן] verb grow fat (Late Hebrew Hiph`il id., also שֶׁמֶן Arabic be fat; Aramaic especially derived species and derivatives; שְׁמֵין adjective fat: Assyrian šammu, fat; Phoenician (Punic) שמן oil, so Palmyrene שמנא Lzb378; on relation of meanings Frä147); —
Qal Perfect2masculine singular שָׁמַ֫נְתָּ Deuteronomy 32:15 and Imperfect3masculine singular וַיִשְׁמַן 32:15 both of Israel (prosperous and arrogant) under figure of fat beast; so Perfect3plural שָֽׁמְנוּ Jeremiah 5:28 (of wicked).
Hiph`il Imperfect3masculine plural וַיַשְׁמִינוּ Nehemiah 9:25 were sated and shewed fatness (inner causative); Imperative masculine singular הַשְׁמֵן Isaiah 6:10 make fat (dull, unreceptive), הַוֶּה הָיָם לֵב.