The story
Said to have been a facetious rendering of the last line of Virgil's Eclogues: "Ite domum saturæ, venit Hesperus, ite capellæ"; or, "Go it, ye cripples, crutches are cheap."
Etymology from Wiktionary, CC BY-SA 4.0.
go it, ye cripples
Today it means: Synonym of go it (“keep it up; term of encouragement”). Full definition →