In a similar fashion to many other Medieval Christian saints, there are nearly no primary sources about Joannicus that are not hagiographical in nature. Byzantine scholars have therefore referred primarily to two hagiographies as the fundamental sources for Joannicius's life. According to those hagiographies, Joannicius was born in 752 in the town of Marikat, into a family of poor swine herders. Joannicius was spiritual from a young age, and often sought solitude in order to pray and contemplate. When Joannicius reached young adulthood, he was drafted into the Byzantine army by Leo IV, and he served honorably, winning the praise of his fellow soldiers. Following his military service of six years, Joannicius desired to enter into a spiritual life and he joined a monastery. Although he wished to immediately retreat to the wilderness, he remained at the monastery for two years, during which time he memorized the Psalms by heart. After two years, he escaped to Mount Uludağ, where he remained as a hermit for the remainder of his life.