Correct spelling for the English word "gisler" is [d͡ʒˈɪslə], [dʒˈɪslə], [dʒ_ˈɪ_s_l_ə] (IPA phonetic alphabet).
The word "gisler" has its etymology traced back to Old High German. It can be traced to the Middle High German word "gisle" or "gissel", which was derived from the Old High German word "gisal" or "gisil". The Old High German word "gisal" was later derived from the Gothic word "gaisla".
In Old High German and Middle High German, "gisler" referred to a hostage or a captive. This word was often used to denote a person who was taken as a pledge of assurance during a time of conflict or as a guarantee of good behavior. Over time, the meaning of the word expanded to include meanings like servant, vassal, or someone in a subordinate position. In modern German, "Geselle" is used for "journeyman" or "assistant".