Do Mandaic's irregularly named letters (halqa, ushenna, it, aksa, in, ash) carry an inherited sense, or are they labels of a different kind?

Most Mandaic letters are named by their own sound with a preceding a (ab, ag, ad...), and their own descriptions state plainly this is a pronunciation label rather than an inherited word with a sense, unlike the Northwest Semitic nouns Hebrew and Syriac kept for the same slots. Six letters break that regular pattern by their own descriptions' own account (Its own text names the set: ushenna, aksa, dushenna, kad and it itself; In and Ash are separately marked as built on a different vowel or sound), and Dushenna and Kad, two of the six, already carry attested senses because they are documented ligatures of a real Aramaic word. The other four, plus Halqa, the very first letter and one of the script's three true vowel signs, whose name is equally outside the regular pattern, have no sense offered by any source consulted, and none of their descriptions states this as a settled absence either.