Well, this page here:
http://www.dacii.ro/modules.php?name=News&file=article&sid=592proposes the Romanian plant name 'Calinul' as the origin of the name Calin. Googling for this plant revealed that this is probably the "European cranberrybush" (Viburnum opulus L.)
But this page here:
http://www.geocities.com/athens/delphi/5647/divtc05.htmtells something else that I was not able to translate. However, it gives a Latin name as origin that does not seem to exist (or contains at least a typo), which is not a sign for reliability and accuracy.
Of course it is also not clear whether the first page is reliable...
Rene www.AboutNames.ch