Where does “bulken” come from?

bulken (Middle English) comes from Middle English balken, from Middle English balke, from Old English balca, from Old Norse balkr, from Proto-Germanic balkô, from Proto-Indo-European bʰelǵ- — to balk, beam.

Ancestry of “bulken”, step by step

Step	Language	Word	Meaning
1	Middle English	balken	to vomit, overflow
2	Middle English	balke	balk, ridge, beam; Alternative form of bakke
3	Old English	balca	balk, beam; bank, ridge; a covering
4	Old Norse	balkr	—
5	Proto-Germanic	balkô	beam, balk
6	Proto-Indo-European	bʰelǵ-	to balk, beam

Every word from Proto-Indo-European bʰelǵ- →Every word from Proto-Germanic balkô →Every word from Old Norse balkr →