I’m a younger speaker from Chicago with some version of a General American accent. I’ve noticed that a small number of words seem to have a nonstandard pronunciation with an inserted lateral sound, probably best represented as [ʟ]. The ones that come to mind are “both,” which might be realized roughly as [bɔ̝ʟθ], and “mouth,” which might be around [maʟθ]. Perhaps the tongue tip might also prepare for the [θ] early, which could create [bɔ̝ɫ̺θ] and [maɫ̪θ], but that is purely hypothetical.
I wonder if any of these pronunciations are common. If they are, in which regions are they most likely to occur, and for what type of speakers? What other words might be realized in a similar way?
I am also searching for an explanation or an underlying rule behind this L-epenthesis. Both examples presented involve the replacement of the endpoint of a closing diphthong before [θ], but I am not sure why that would facilitate the insertion of a lateral sound or if that is the only situation in which it is possible.