mother (n.1)
Old English modor "female parent," from Proto-Germanic *mothær (cognates: Old Saxon modar, Old Frisian moder, Old Norse moðir, Danish moder, Dutch moeder, Old High German muoter, German Mutter), from PIE *mater- "mother" (cognates: Latin mater, Old Irish mathir, Lithuanian mote, Sanskrit matar-, Greek meter, Old Church Slavonic mati), "[b]ased ultimately on the baby-talk form *mā- (2); with the kinship term suffix *-ter-" [Watkins]. Spelling with -th- dates from early 16c., though that pronunciation is probably older (see father (n.)).

Mother nature first attested c.1600; mother earth is from 1580s. Mother tongue "one's native language" first attested late 14c. Mother of all ________ 1991, is Gulf War slang, from Saddam Hussein's use in reference to the coming battle; it is an Arabic idiom (as well as an English one), for instance Ayesha, second wife of Muhammad, is known as Mother of Believers. Mother Carey's chickens is late 18c. sailors' nickname for storm petrels, or for snowflakes. Mother lode attested by c.1882, from mining [1849].
mother (v.)
1540s, "to be the mother of," from mother (n.1). Meaning "to take care of" is from 1863. Related: Mothered; mothering.
mother (n.2)
"a thick substance concreting in liquors; the lees or scum concreted" [Johnson], probably from Middle Dutch modder "filth, dregs," from PIE *meu- (see mud).