Abstract This article investigates the genesis and diachronic persistence of ‘overabundance’ (Thornton 2011) or variation at the level of individual cells in a lexeme’s paradigm (e.g. Italian pst.ptcp forms sepolto/seppellito ‘buried’). Two main genetic paths are identified: emergence (i) via form competition (e.g. Italian ella/essa ‘she’) and (ii) via rule competition (e.g. Ladin talaranes/talarane/talaràs ‘spiders’). Building on previous work (Cappellaro 2013, 2017), the present study proposes that persistence correlates positively with low frequency and later acquisition, but also addresses the question whether there is a link between genetic type (form/rule competition) and persistence. In the case of Italian sepolto/seppellito < Latin sepultus/sepelitus, persistence over millennia is metachronic – a function of analogical pressures inherent in the system, which can, in principle, operate at any given time.