Praise be to Allah.
Aymaan is the plural of yameen, which may mean:
1.Hand, as in the verse in which Allah says (interpretation of the meaning) “that your right hands (aymaanukum) possess” [al-Nisa ‘ 4:3 and elsewhere].
2.Oath or vow, as in the verse in which Allah says: “And protect your oaths [aymaanakum] (i.e. do not swear much)” [al-Maa’idah 5:89]
Based on that, it is not appropriate to call the child Aymaan, because it makes no sense to call the child by the word that is the plural for hands or oaths!
And Allah knows best.