or else, or suffer the consequences: Do what I say, or else.
Origin of else
before 1000;Middle English,Old Englishelles (cognate with Old High Germanelles), equivalent to ell- other (cognate with Gothicaljis,Latinalius,Old IrishaileGreekállos, Armenian ayl other; cf. eldritch) + -es -s1
The possessive forms of somebody else,everybody else, etc., are somebody else's, everybody else's, the forms somebody's else, everybody's else being considered nonstandard in present-day English. One exception is the possessive for who else, which is occasionally formed as whose else when a noun does not immediately follow: Is this book yours? Whose else could it be? No, it's somebody else's.
Old English elles "other, otherwise, different," from Proto-Germanic *aljaz (cf. Gothic aljis "other," Old High German eli-lenti, Old English el-lende, both meaning "in a foreign land;" see also Alsace), an adverbial genitive of the neuter of PIE root *al- "beyond" (cf. Greek allos "other," Latin alius; see alias). Synonym of other, the nuances of usage are often arbitrary.
Productive of a number of handy compounds that somehow never got traction or have been suffered to fall from use: elsehow (1660s) "somehow or other;" elsewards (adv.), 1882, "somewhere else;" Old English elsewhat (pron.) " something else, anything else;" elsewhen (adv.), early 15c., "at another time; elsewhence (c.1600); elsewho (1540s). Among the survivors are elsewhere, elsewise.