古英語のself, self, selfから、原ゲルマン語の*selbaz, selfから、PIEの*sel-bho, 反射代名詞の語源である*swe, selfの拡大形、語源はswain, customと同じ。
Trying to define yourself is like trying to bite your own teeth. [Alan Watts]Its use in compounds to form reflexive pronouns grew out of independent use in Old English. As a noun from early 14c.