Where does “si” come from?

si (Papiamentu) comes from Spanish sí, from Old Spanish sy, from Latin sīc, from Latin sice, from Latin sī, from Proto-Italic sei, from Proto-Indo-European só — this; that.

si (Papiamentu): if; when; yes

Definitions

if; when; yes

Ancestry of “si”, step by step

si traces back through two separate lines of ancestry.

via Spanish sí

Step	Language	Word	Meaning
1	Spanish	sí	yes, affirmation. Commonly used to respond...
2	Old Spanish	sy	yes in response to a question
3	Latin	sīc	yes, indeed (If answering a question)
4	Latin	sice	—
5	Latin	sī	if, supposing that
6	Proto-Italic	sei	so, thus
7	Proto-Indo-European	só	this; that

via Portuguese sim

Step	Language	Word	Meaning
1	Portuguese	sim	yes; indeed; do; yes; yea
2	Old Portuguese	si	yes, affirmatively
3	Latin	sibi	the dative of the reflexive pronoun meaning to...
4	Proto-Indo-European	sébʰye	—
5	Proto-Indo-European	swé	self

Every word from Proto-Indo-European só →Every word from Proto-Italic sei →Every word from Latin sī →