Lam negates the imperfect with past-time reference and places it in the jussive. Takallam(i) belongs to the root k-l-m and the derived pattern tafaʿʿul, related to takallum, speaking. Here the verb is assigned to a place; it is not a literal claim that the dwelling once used language.
The final kasrah in poetic performance relates to sound and metre, not to a different normal grammatical case for the verb. The attribution of speech to ruins is a form of personification: the speaker seeks an answer from a place that can no longer give one.