Where does “como não” come from?

como não (Portuguese) comes from Portuguese como, from Old Portuguese como, from Latin comō, from Latin quōmodo, from Latin quō, from Latin quī, from Latin -cumque, from Latin cumque — to bend; curve; arch; vault; to bow, bend, arch,...

como não (Portuguese): yes

Definitions

Ancestry of “como não”, step by step

como não traces back through two separate lines of ancestry.

via Portuguese como

Step	Language	Word	Meaning
1	Portuguese	como	how in what way, manner
2	Old Portuguese	como	how
3	Latin	comō	to bring together, form, frame, construct, arrange
4	Latin	quōmodo	in what manner or way?; how?
5	Latin	quō	whither, whereto, where
6	Latin	quī	who, that, which, what
7	Latin	-cumque	Used to derive indefinite adjectives, adverbs and...
8	Latin	cumque	however, whenever, howsoever, whensoever
9	Latin	cum	with, along with; at; -fold
10	Old Latin	com	Alternative form of cum
11	Proto-Italic	kom	with, along, at
12	Proto-Indo-European	ḱóm	beside, near, by, with
13	Proto-Indo-European	ḱe	Deictic particle, here; Post-positional...
14	Middle English	kyt	—
15	German	kitt	putty certain kinds of cement used for fixing e.g. window panes
16	Old High German	kuti	—
17	Proto-West Germanic	kwidu	gum, resin
18	Proto-Germanic	kweduz	resin
19	Proto-Indo-European	gʷet-	resin, gum; to say, speak
20	Proto-Indo-European	gū-	to bend; curve; arch; vault; to bow, bend, arch,...

via Portuguese não

Step	Language	Word	Meaning
1	Portuguese	não	not; do not; have not; non-; isn't it? right?
2	Old Occitan	non	—
3	Latin	nōn	not
4	Old Latin	noenum	—
5	Proto-Indo-European	óynos	one; single

Every word from Proto-Indo-European gū- →Every word from Proto-Indo-European gʷet- →Every word from Proto-Germanic kweduz →