أَيِ الِالْتِزَامُ اللُّزُومَ الذِّهْنِيَّ
That is, the relevant necessity for iltizām is a mental entailment.
The signified concomitant lies outside the term's assigned meaning, but there must be a connection through which apprehending the primary sense leads the mind toward the other. Merely finding the two things together by coincidence in the external world does not establish this kind of indication.
A classical logical illustration moves from the essential conception of “human” to the characteristic capacity for laughter. That capacity is not an internal element of the essential definition in the same way as “animal” or “rational,” but is treated as a connected property.