The roots *h₂ep- (“(body of) water”) and *h₁egʷʰ- (“drink”) are probably unrelated. A connection to *h₁eḱ- (“swiftness, celerity”) has been proposed, in which case the semantic development would be "that which is swift" > "river" (as attested in Germanic) > "water" (as in Latin).
|Thematic in *-eh₂|
- Proto-Germanic: *ahwō (“water”) (see there for further descendants)
- Proto-Italic: *akʷā (see there for further descendants)
- Lusitanian: aqua (“river”)