How did Islamic calligraphy start?

18th century writing in Ottoman calligraphy. Depicts the phrase 'In the name of God, Most Merciful, Most Gracious'

Islamic calligraphy, also known as Arabic calligraphy, is the artistic practice of handwriting, or calligraphy, and by extension, of bookmaking,[1] in the lands sharing a common Islamic cultural heritage. This art form is based on the Arabic script, which for a long time was used by all Muslims in their respective languages. They used it to represent God because they denied representing God with images.[2] Calligraphy is especially revered among Islamic arts since it was the primary means for the preservation of the Qur'an. Suspicion of figurative art as idolatrous led to calligraphy and abstract depictions becoming a major form of artistic expression in Islamic cultures, especially in religious contexts.[3] The work of calligraphers was collected and appreciated.

Arabic, Persian and Ottoman Turkish calligraphy is associated with abstract arabesque motifs on the walls and ceilings of mosques as well as on the page. Contemporary artists in the Islamic world draw on the heritage of calligraphy to use calligraphic inscriptions or abstractions in their work. Hope this helps!, btw i got it off wiki :)