In the discussion of wholly and holy (blog, 30 October) I didn’t touch on the question of whether wholly is pronounced with one l sound or two (though some commentators did). So let’s do so now.
The general rule in English is that when you form an adverb in -ly from an adjective ending in l you simplify the two l sounds to one. Thus fully is ˈfʊli, partially is ˈpɑː(r)ʃəli. In addition, in an adverb formed from a stem ending in syllabic l the syllabicity is lost, thus simple, simply ˈsɪmpl̩, ˈsɪmpli, gentle, gently ˈdʒentl̩, ˈdʒentli (though there is some hesitation for subtly ˈsʌt(l̩)li). The ending -ically, too, usually has the underlying -ɪkəlli compressed to simple -ɪkli, thus physically ˈfɪzɪkli.
This means that for wholly we would normally expect only a single l sound. Does the fact that some speakers sometimes pronounce a double (geminated) l imply that they are treating this word as an exception, perhaps consciously striving to differentiate it from holy or hole-y? Perhaps it does. On the other hand, when we form a nonce -ly adverb from an adjective that is not usually made into an adverb in that way, double l may be preserved: you can experiment with dully ˈdʌl(l)i, smally ˈsmɔːlli, and futilely BrE ˈfjuːtaɪlli.
With the suffix -less there is no such simplification: guileless is ˈɡaɪlləs, not *ˈɡaɪləs; similarly tailless, soulless.