ea (n.)

the usual Old English word for "river, running water" (still in use in Lancashire, according to OED), from Proto-Germanic *ahwo- (source also of Old Frisian a,Old Saxon aha,Old High German aha,German ahe-,Old Dutch aha,Old Norse "water"), from PIE root *ekweh- "water" (see aqua-). "The standard word in place-names for river denoting a watercourse of greater size than a broc or a burna" [Cambridge Dictionary of English Place-Names].