One movement underlies this big family: coming inside, gathering in. When one person enters, it is כְּנִיסָה; when many are gathered into one place, it is a כֶּנֶס, a congress, and the assembly of the whole nation is the כְּנֶסֶת. Push the root into the causative and "bring in" becomes הַכְנָסָה, what you bring into your pocket: income. Even the trousers (מִכְנָסַיִם) are the garment you step into. From a doorway to a parliament to your salary, the thread is the same inward gathering. Every word here is verified against pealim, niqqud included.
The same root runs through the verb system. Each binyan is a voice: it bends the one idea into active, passive, causative or reciprocal. Tap to hear.
This root has no everyday pa'al: plain "to enter" is the nif'al לְהִכָּנֵס, where the actor goes in. The pi'el לְכַנֵּס gathers others together, and the causative hif'il לְהַכְנִיס puts something inside. Notice how the three live voices map onto the family: one enters (nif'al), one assembles (pi'el), one brings in (hif'il).
Same root letters, different noun moulds (mishkalim). The mould tells you the function: who does it, the act of doing it, or the thing produced.
Strip the prefixes, suffixes and vowels. Three consonants remain, and the meaning lives there.