Where does “הי״ד” come from?

הי״ד (Hebrew) comes from Hebrew ה׳ יִנקּוֹם דָּמוֹ — may Hashem avenge his blood.

Ancestry of “הי״ד”, step by step

Step	Language	Word	Meaning
1	Hebrew	ה׳ יִנקּוֹם דָּמוֹ	may Hashem avenge his blood

הי״ד — Etymology, Origin & Word History | Etymology Explorer