From en.wiktionary.org:
** English
*** Alternative forms
- [en]
*** Etymology
From [en] (Modern [fr]).
*** Adverb
[-]
1. From head to toe , especially of armor or other military accoutrements.
2. * 1661–67 , [Abraham Cowley] , _Basa Sunda: Essays (Cowley)/The Dangers of an Honest Man in much Company_ :
3. *: If twenty thousand naked Americans were not able to resist the assaults of but twenty well-armed Spaniards, I see little possibility for one honest man to defend himself against twenty thousand knaves, who are all furnished CAP-A-PIE with the defensive arms of worldly prudence, and the offensive, too, of craft and malice.
4. * 1808–10 , [William Hickey (memoirist)] , _Memoirs of a Georgian Rake_ , Folio Society 1995, p. 129:
5. *: I sallied forth CAP-À-PIE in my Madras regimentals, intending to accompany Brent to Westminster Abbey, and to take a coach at the first stand we came to.
6. * [en]