为什么这里要使用被动given呢？

Strickland was impossible, and he swore never to speak to him again. But the season touched him with gentle feeling, and he hated the thought of Strickland spending Christmas Day by himself; he ascribed his own emotions to him, and could not bear that on an occasion given up to good-fellowship the lonely painter should be abandoned to his own melancholy. Stroeve had set up a Christmas-tree in his studio, and I suspected that we should both find absurd little presents hanging on its festive branches; but he was shy about seeing Strickland again; it was a little humiliating to forgive so easily insults so outrageous, and he wished me to be present at the reconciliation on which he was determined.

这里 on an occasion given up to good-fellowship：没理解given up to 什么含义？尤其是为什么这里要使用被动given呢？