English word alga comes from Proto-Indo-European *alǵ-

Detailed word origin of alga

Dictionary entry	Language	Definition
*alǵ-	Proto-Indo-European (ine-pro)	to be dirty, be slimy; frog; duckweed
algam	Latin (lat)
alga	English (eng)	(biology) Any of many aquatic photosynthetic organisms, including the seaweeds, whose size ranges from a single cell to giant kelps and whose biochemistry and forms are very diverse, some being eukaryotic.

Words with the same origin as alga