Where does “galga” come from?

galga (Old English) comes from Frankish galgō, from Proto-Germanic galgô, from Proto-Indo-European ǵʰAlgʰ-.

Ancestry of “galga”, step by step

Step	Language	Word	Meaning
1	Frankish	galgō	measuring rod, pole; gallows
2	Proto-Germanic	galgô	a rod, pole, stake; a beam, cross-beam, rafter; a...
3	Proto-Indo-European	ǵʰAlgʰ-	—

galga — Etymology, Origin & Word History | Etymology Explorer