A stock phrase in Japanese pop culture supposedly used by the wife in a newly-wed couple to invite her new husband to bed.

Kyūjitai form of 私生児 (“illegitimate child”)

If one learns without thinking, one will be lost in his learning. That is, if one does not think about what one learns, he will not arrive at the truth of it.

(medicine) zoonosis, more specifically, amphixenosis: a disease that can infect both humans and animals