Meaning

noun informal terms for nakedness

adverb to a complete degree or to the full or entire extent (`whole' is often used informally for `wholly')

adverb with everything included or counted

originFrom Middle English altogeder, altogedere, equivalent to al- (“all”) + together. Cognate with Scots awthegither (“altogether”), Middle High German alzegater (“altogether”), Dutch altegaar. Compare also Old English ealġeador, eallġeador (“altogether”), West Frisian allegearre (“altogether”). More at together. The noun sense (nakedness): was popularized in George du Maurier's 1894 novel Trilby.

Etymology from Wiktionary, CC BY-SA 3.0