Nidus literally means "nest" in Latin, and some of its relatives in English suggest this connection in a straightforward way. For example, we have
nidification for the process of building a nest, and
nidicolous, meaning "reared in a nest." But
nidus itself, when used as an English word, is apt to refer to a place where bacteria lodge and multiply. Consequently, the extended use of
nidus in English often has a negative connotation referring to a source of undesirable opinions or behaviors.