Where does “upswarm” come from?

upswarm (English) comes from English swarm, from Middle English swarm, from Old English swearm, from Proto-Germanic swarmaz, from Proto-Indo-European swēr- — heavy.

upswarm (English): To rise in a swarm; To cause to rise in a swarm

Definitions

To rise in a swarm; To cause to rise in a swarm

Ancestry of “upswarm”, step by step

upswarm traces back through two separate lines of ancestry.

via English swarm

Step	Language	Word	Meaning
1	English	swarm	A large number of insects, especially when in...
2	Middle English	swarm	A swarm; A large group of people
3	Old English	swearm	swarm
4	Proto-Germanic	swarmaz	swarm; dizziness
5	Proto-Indo-European	swēr-	heavy

via English up

Step	Language	Word	Meaning
1	English	up	Away from the surface of the Earth or other...
2	Middle English	up	to a vertical axis
3	Old English	upp	up; upstairs
4	Proto-West Germanic	*upp	—

Every word from Proto-Indo-European swēr- →Every word from Proto-Germanic swarmaz →Every word from Old English swearm →