For Western laymen starting the Buddhist studies, I highly suggest the New Horizons series book Jean Boisselier, The Wisdom of the Buddha, 1993 (available for example from here). Merely by reading that short version of Buddha's life biography, I felt instant wait-a-minute... moments of eery similarities to life biographies of Jesus Christ and prophet Muhammad, on which element the late Danish Buddhism researcher Christian Lindtner wrote much on. From that above book on Buddha one reads:A child was born there [Buddha]; his mother was the daughter of a king, and his father was a high priest. To avoid shame, they had to deny their own blood.
[...] On his travels, he met a Frya steersman who had been enslaved; from him he learned about our morals and traditions. He bought his freedom and they remained friends till death. Everywhere he went, he taught the people that they should not tolerate rich men or priests, and that they must take heed against imposed shame, which inevitably sullies love.
[...] His first name was Yesus, but the priests, who despised him, called him Fo, that is ‘false’. The folk called him Krisen, that is ‘herdsman’ [Krishna the herdsman] and his Frya friend called him Buda, that is ‘pouch’, because he had in his head a treasure of wisdom, and in his heart a treasure of love. (Source OL MS 137-138)
Here above we have the core of the Frisian Buddha biography's beginning part, but pushed in the Buddhist account into further past lives. The Frisian version makes more sense, as it pertains directly to the life biography of the main hero of the tale. The story continues:Here, the Boddhisatva [Buddha's previous incarnation] was born as Prince Vessantara (Viśãntara, in Sanskrit), son of the king of the land of Sivi. [...] Vessantara married the princess Maddĩ, herself equally given to meritorious acts. Together they had two children. [...] Jũjaka, an old and disreputable brãhman, came to demand Vessantara's children to be used as slaves for Jũjaka's young wife. This gift of one's own offspring, a gift superior to all others, could not be refused. [...] Meanwhile, the king of Sivi was able to buy back his grandchildren from Jũjaka, who ten died in a state of debauchery.
[...] As King Śuddhodana and Queen Mãyãdevĩ [Buddha's mother] were without children and had practised abstinence, the conception of the Bodhisattva was believed to be immaculate.
(Source: Jean Boisselier, The Wisdom of the Buddha, 1993, p. 32-35, 39)
Upãli is an eastern form of the names Apollo, Apollonius and Frisian names Apol (A.POL, ÁPOL) and Apollonia (A.POL.LÁNJA). Any enslaved European person would have automatically belonged to the lowest śũdra class:The Buddha was now in his thirty-sixth year. During the next forty-five years, until his Total Exctinction, he traveled through the middle basin of the Ganges accompanied by his disciples, begging his daily food and spreading his Teaching without discrimination. [...]Interestingly, the two travelling merchants who became the first converts may not even have been of Indian origin. [...] Soon, the addition of Upãli, a sũdra (from the servant class), who would prove to be a major disciple, shows the degree to which Buddhism was established outside the caste system.
[After Buddha's death, an early Buddhist convent meets to discuss what to do with their late master's legacy] Questions related to points of Disciple (vinaya) we directed to Upãli, the former barder of the Śakyas.
(Source: Jean Boisselier, The Wisdom of the Buddha, 1993, p. 78-80, 117)
brãhman (priest class,)
kshatriya (warrior class)
vaisýa (farmer class)
śũdra (non-Aryan Indians, fallen members).
The barber is an ancient profession and is attested also from European context e.g. Greek barber shops. Thus from quick reading, it seems that "Upãli" the servant barber would be the first candidate for Buddha's Frisian friend. Read more here and here of how he was the caste system breaking figure in Buddhism and also judged suits based on spiritual merit and not on lineage - it all reads rather Frisian to my mind. Just as OL MS Buddha's origins seem to have been pushed to the past lives in the Buddhist version, this "Upãli's" past lives include "that Upāli had been an all-powerful wheel-turning king for thousand previous lives" - a turner of a Frisian Jol wheel in his youth..?