Where does “Delannoy” come from?

Delannoy (French) comes from Old French dé, from Latin dadu, from Latin datum, from Latin datus, from Latin dāre, from Proto-Italic didō, from Proto-Indo-European dédeh₃ti, from Proto-Indo-European deh₃- — to give.

Ancestry of “Delannoy”, step by step

Delannoy traces back through two separate lines of ancestry.

via Old French dé

Step	Language	Word	Meaning
1	Old French	dé	die
2	Latin	dadu	—
3	Latin	datum	gift, present; accusative supine of dō;...
4	Latin	datus	given; offered; yielded
5	Latin	dāre	—
6	Proto-Italic	didō	give
7	Proto-Indo-European	dédeh₃ti	to be giving
8	Proto-Indo-European	deh₃-	to give

via Old French Lannoy

Step	Language	Word	Meaning
1	Old French	Lannoy	—
2	Latin	alnētum	—
3	Latin	alnus	An alder; Anything made of alder wood; a ship,...
4	Proto-Italic	alznos	—
5	Proto-Indo-European	h₂élsnos	alder
6	Proto-Indo-European	h₂élis	—

Every word from Proto-Indo-European deh₃- →Every word from Proto-Indo-European dédeh₃ti →Every word from Proto-Italic didō →