Complex sentence: Sligo is an English corruption of the Irish name "Sligeach"--meaning "abounding in shells"--referring to the abundance of shellfish found in the river and its estuary, and from the extensive'shell middens' in the vicinity.
Split into simpler sentences: Sligo is an English corruption of the Irish name "Sligeach", meaning "abounding in shells" or "shelly place". This refers to the abundance of shellfish found in the river and its estuary, and from the extensive'shell middens' in the vicinity.