It's such a pity that dyad is a "stupid" word, because it has quite a few sibling words. For example, monad (fr. L monas 'unit', monadis, fr. Gk μονος monos 'one'); dyad (fr. Gk duas, duados); triad; tetrad; pentad; hexad; heptad; octad (but also note ogdoad); ennead; and decade.
Here you have words for groups of N from one to ten. Why make it a suppletive set of words. Use dyad, instead of pair, when it is quite possible to use other groups of N words. Nice how decade originally meant a group of ten anything, and not just years. We have cardinal numbers, for counting, and ordinal numbers for ordering, then why not, I ask you, group numbering for denoting groups of things.
It also occurs to me that since pair is ultimately from Latin, and a loanword in English, what perfectly good native word got forced out of the word hoard.
—Ceci n'est pas un seing.
Yes, I am with you zmj. Imagine however, the look on shop assistants' faces when you want to buy a dyad of pants. Or, a dyad of trousers. I wonder how many legs you would get.