Where does “staunchly” come from?

Staunchly comes from Middle English -ly, Old French estanche, Proto-Germanic -līkaz and galīkaz, and Proto-Indo-European līg- and ḱóm.

staunchly (English): In a staunch manner

Definitions

Step	Language	Word	Meaning
1	English	staunch	Loyal, trustworthy, reliable; Dependable,...
2	Middle English	staunche	—
3	Old French	estanche	firm, watertight
4	Old French	estanc	pond
5	Old French	estanchier	to staunch
6	Vulgar Latin	stanticare	to make stagnant
7	Latin	stānticus	—
8	Latin	stāns	—
9	Latin	stō	—
10	Proto-Italic	staēō	stand
11	Proto-Indo-European	sth₂éh₁yeti	—
12	Proto-Indo-European	*steh₂-	—