The linguistics here are going over my head, but so far as samādhi, I wrote a short essay on that:
As for translation idioms, typically we try to avoid using terms that invoke specific religious connotations. For example, we prefer “talk” to “sermon” or “teach” to “preach”. Like all rules of translation, it is just a rough guidleine, for example I use “sabbath” for uposatha.
The reasons for avoiding “churchy” terms are historical and cultural, and may not apply in a different context. The Buddha himself adopted many “religious” terms, often redefining them, but in other cases he developed a new vocabulary.