Almost always appears inside the pattern X
是 哪 学来 的? — '(it is) from-where learned?'. The
来 is a directional/result complement implying 'come to know/acquire'. Casual register, often spoken with surprise or mild disapproval. The fuller form
从哪儿学来的 (cóng nǎr xué lái de) is more common in writing.
