The origin of the name

The origin of the name "Killeen"
Derivation from the Irish	"Killeen" is the anglicised version of the Irish Surname "Ó Cillín", (pronounce "O Killeen"), which, in the female version, may be changed to "Uí Chillín" (pronounce "Ee Killeen") for a woman's married name, or "Ní Chillín" (pronounce "Nee Killeen") for an unmarried female. The prefix "Ó" means "From," i.e., "Descended From." "Uí" is the genitive (or possessive) case of "Ó", indicating "(wife) of the descendant of", while "Ní" is a shortened form of "Iníon Uí", or "daughter of ."
Meaning: "Cill" + "ín"	The suffix "ín" (pronounce "een") means "small." "Cill" or "Ceall" originally meant "cell," and then extended in meaning to "church," "church-yard" and "grave-yard," as well as "treasure-box," "nest-egg" and "treasure." In the "grave-yard" context "Cillín" (and its English version "Killeen") came to mean the small "cill" or burial-ground, outside of the consecrated grave-yard, where unbaptised infants were buried. This is often its meaning in placenames. However, as a surname, it may, also, derive from another word "ceall" meaning a row or dispute, to which the diminutive "ín" (pronounce "een") is added, indicating a clan of people given to little disputes. (The name "Kelly" can have the same origin, the "ach" at the end of its Irish version, "Ceallach", having the same meaning as the "ín" at the end of "Cillín", and "Ceall" being the root of the word "Cill"). A more likely origin of the surname "Killeen," in most cases, is as a patronymic meaning "Descendant of Cillín," the name "Cillín" occurring here as a first-name, meaning "treasure."
"Cillín" as a First-name	Like most Irish surnames, "Killeen" can, also, occur as a first-name, in which case the anglicised version is usually spelt "Killian." Saint Killian was an Irish Saint who brought Christianity and literacy to Germany in the 5th century. An illuminated manuscript attributed to him in Salsburg Cathedral is reputed to be more beautiful than the Book of Kells. A parent who called his child "Cillín" no doubt intended the "little treasure" meaning, rather than the alternative meanings, such as "little disputant."
Surnames in Ireland	Surnames came into vogue in Ireland in response to a directive from the Pope in the 11th century. The patronymics of previous centuries, such as Mac Dónaill (son of Donal), or Ó Dónaill (descendant of Donal) then became fixed surnames. Thus, some of the descendants of Brian Boru became "O'Briens" ("descended from Brian"), while others became MacMahons ("son of Mahon," who was himself a grandson of Brian). Since Irish surnames derive from Christian names which were in use in the 11th century, there are usually several different clans of the same name.
Killeens in Lusmagh	An English family named "Churchill" who settled in the parish of Lusmagh in County Offaly (from which the writer's family hail) a couple of centuries ago adopted the surname "Killeen" in order to blend with the local culture. There are, apparently, three branches, originally unrelated, of Killeens in Lusmagh.