Old Irish loch

← Breton loc'h (cognate)

← Proto-Celtic *loku (inherited)

← Welsh llwch (cognate)

← Proto-Indo-European *lókus (inherited)

← Cornish logh (cognate)

→ English lough (derived)

→ Old English lagu (cognate)

→ Irish loch (inherited)

→ Scottish Gaelic loch (inherited)

→ Ancient Greek λάκκος (cognate)

→ Manx logh (inherited)

→ Old Irish Glenn Dá Locha (compound)