I am curious about the origin of West Germanic geminated voiced stops that do not arise from a following *j, as in Old English crabba, stagga, frogga, codd, stubb, Old Norse klubb, Old Saxon roggo, etc. Are these purely expressive geminations, or are they regular phonological developments of *b, *d, *g (< *bh, *dh, *gh/g'h or *p, *t, *k/k'?) plus *n, or something else? I thought primitive Germanic only had unvoiced geminated stops, and I thought that any IE stop plus *n yielded Germanic geminated voiceless (only) stops. Also why does dd seem to be rarer than bb or gg?
Andrew