Outremer has a very mixed and culturally diverse population, and thus the languages used are diverse as well. Some languages are European, others Semitic, and others asian Indo-European. Some are not to be found in our world at all.
Arabic is the most commonly used language, thanks to the influence of the Koran. All Muslims are encouraged to read the Koran in its native Arabic, and thus non-Arab Muslims can speak and read Arabic in addition to their native Turkic or Kurdish languages. From this position of advantage, it has become used as a second language throughout Outremer, mostly displacing Aramaic in Muslim areas.
Aramaic, a Semitic language related to Arabic and Hebrew, is spoken mostly by Jews in Outremer, as Hebrew is a sacred tongue used in the synagogue rather than a living tongue. Some Syrian Muslims and Christians also speak it, though Arabic is the main language of these groups. It is widespread, but never spoken as the majority language.
Frankish, or Lingua Franca, is the language of most of the European-descended inhabitants. It is derived from Old Langued'oui French, some German, and Italian, and with many Arabic loan words. Related is Edessan, which is derived from Langued'oc French, because most of the settlers were Aquitanians and Angevins, from when Eleanor of Aquitaine was its Princess. Edessan has many Arabic and Kurdish loan words, and a strong Armenian element as well. it is spoken widely in Edessa and Armenia.
Armenian, a native Indo-European language, is spoken mostly in Armenia and Edessa, with a strong presence as well in Jerusalem.
Bohemian is a dialect of Czech and Slovak spoken only in Cyprus. It is a Slavic language, with many Greek and German loan words.
Turkish - an Altaic turkic language, is the language of the Turks, spoken in Edessa and the Othmanli Sultanate, as well as parts of Rhodes and Armenia.
Kurdish is the language of the Kurds, an Indo-European language. It is spoken mostly in Edessa, but also in Armenia and the Othmanli Sultanate.
English is spoken only in Acre and parts of Damascus.
Many Outremer natives are fluently multilingual, with most of those who are not at least bilingual, and which languages they speak natively - that is without taking the Linguistics skill - will be up to the GM.