dofonaig
Old Irish
    
    Etymology
    
Formed with dí- + fo-. The verb stem cannot be nigid directly, since it would have resulted in a *do·fuinig via raising and palatalization of the -n-. Uhlich believes that the lack of palatalization arose under influence of related verbal nouns like fonach.[1]
Uhlich assumes that the verbal nouns were formed from an o-grade stem *noig-. Given how root-based neuter o-stem nouns are generally formed with the e-grade and zero-grade and not the o-grade, Gordon instead believes that the verbal noun's stem was either e-grade *nēg- or zero-grade nig-.[2] Díunach itself gives no indication of which, since palatalization would have been lost anyway due to syncope of the o in fo-. Both fonach and funech exist in Early Irish, meaning they are of no help either in finding out which stem grade the verbal nouns originally used.
Inflection
    
| 1st sg. | 2nd sg. | 3rd sg. | 1st pl. | 2nd pl. | 3rd pl. | Passive sg. | Passive pl. | ||
|---|---|---|---|---|---|---|---|---|---|
| Present indicative | Deut. | do·fonuch; do·fonug | do·fonget | ||||||
| Prot. | |||||||||
| Imperfect indicative | Deut. | ||||||||
| Prot. | |||||||||
| Preterite | Deut. | ||||||||
| Prot. | |||||||||
| Perfect | Deut. | ||||||||
| Prot. | |||||||||
| Future | Deut. | do·fonus | |||||||
| Prot. | |||||||||
| Conditional | Deut. | ||||||||
| Prot. | |||||||||
| Present subjunctive | Deut. | ||||||||
| Prot. | |||||||||
| Past subjunctive | Deut. | ||||||||
| Prot. | |||||||||
| Imperative | |||||||||
| Verbal noun | díunach, díunnach, díunag | ||||||||
| Past participle | |||||||||
| Verbal of necessity | |||||||||
Mutation
    
| Old Irish mutation | ||
|---|---|---|
| Radical | Lenition | Nasalization | 
| do·fonaig | do·ḟonaig | do·fonaig pronounced with /-v(ʲ)-/ | 
| Note: Some of these forms may be hypothetical. Not every possible mutated form of every word actually occurs. | ||
References
    
- Uhlich, Jürgen (1995), “On the Fate of Intervocalic *-ṷ- in Old Irish, Especially between Neutral Vowels”, in Ériu, volume 46, Royal Irish Academy, →ISSN, →JSTOR, retrieved August 26, 2022, pages 11–48
- Gordon, Randall Clark (2012) Derivational Morphology of the Early Irish Verbal Noun, Los Angeles: University of California, page 260
Further reading
    
- G. Toner, M. Ní Mhaonaigh, S. Arbuthnot, D. Wodtko, M.-L. Theuerkauf, editors (2019), “do-fonaig”, in eDIL: Electronic Dictionary of the Irish Language