Output optimization in the Irish plural system

In this paper I argue that a subpattern of Irish plural allomorphy should be analyzed as output optimizing in character. Specifically, I claim that stress-sensitive alternations between the plural suffixes -(e)anna and -(e)acha are conditioned by constraints on metrical well-formedness. This analysis connects with independent facts about the the prosodic prominence of [ax] sequences in Irish phonology. I further argue that an explanatory analysis of these patterns must make use of the notion of surface optimization. Alternative frameworks that eschew surface-oriented optimization mechanisms fail to account for synchronic and diachronic properties of the Irish plural system.