More rare initial pairs of letters for roots - with fewer than five roots each

 There are a lot of single usage roots (233 outside of the domain of Names) and single usage words (19,772) in the Hebrew Bible, far more than I have time to look at. Rather, I want to limit the low-usage words to those where the first two letters of the root are also rare.

There are only 29 such pages in the concordance.

ay(3)

aq(1)
h(1)
hk(3)
hc(1)
hx(1)
hq(1)
hw(1)
vh(1)
vi(1)
vn(1)
vp(1)
zg(1)
zz(1)
'ta(3)
't't(3)
ld(4)
lt(1)
m(4)
nl(1)
s't(2)
ss(2)
ya(2)
qt(4)
wx(1)
tg(3)
td(4)
tz(1)
tt(4)

This is not too many and it further explores the letter combinations that are avoided in the first two letters of a root. Some of these we have already met in the past few posts on Hebrew roots. (All the references are at the links)

ay(3) is the unique timber from my first post in the series.
aq(1) is the ibex.
h(1) is the emphatic separation of the definite article from its word.
hk(3) is a rarely used name.
hc(1) insult, used once in Job. It is a hapax in my translation also (of course).
hx(1) is a rarely used name. So is hq(1), and hw(1)
vh(1) likewise as well as vi(1), vn(1), and vp(1)
zg(1) is husk - another hapax.
zz(1) is a rarely used name.
'ta(3) is the Aramaic for good.
't't(3) frontlets. 
ld(4) is a rarely used name.
lt(1) a measure, a bit more of.
m(4) only four times is this prefix connected only to a pronoun.
nl(1) a benefaction.
s't(2) is a rarely used name. So is ss(2)
ya(2) the unique wood from the first post.
qt(4) zither.
wx(1) another measure - a smidgen.
tg(3) is a rarely used name. As are those at td(4)
tz(1) lopped.
tt(4) is a rarely used name.

Now the challenge is to assimilate all this detail about the letters and see if there is an explanation or two as to why in Hebrew certain sequential sounds are avoided.