Humayl, also written as Humail, is an ancient Arabic name for boys with uncertain meaning. It is derived from the H26-M-L root which has meaning of "water flowing without obstruction", "rain falling silently". It is not a Quranic name directly or indirectly, but since it doesn't have a bad meaning Muslims can use it. Humayl was the name of a Sahabi (companion of the Prophet, peace and blessings of Allah upon him and his companions), whose full name was al-Humayl bin ad-Damoun, and this is the reason why some people use this name for their children.
Humayl is pronounced [(H)ot + p(U)t] + [(MAY) + p(L)ay] and is written as هُمَيْل in Arabic.
A related name is Hummaal, which is a synonym of Humayl and similar to it in meaning and origin, though it doesn't seem to be a Sahabi name.