Searching online I came across a nice article which wrote: link
It is a teaching of Chassidic thought (the only source I have for this is Shlomo Carlebach!) that the first occurrence of a certain phrase in Tanach is (as Reb Shlomo said) the “headquarters.” Something profound can be learned from the fact that a certain phrase or word occurs first in a certain context.
And also: http://www.orchos.org/vol-1---11.html:
'Rav Tzadok HaCohen explains that wherever a letter or word appears for the first time in the Torah the context in which the letter or word appears defines its deepest meaning.'
I wondered where this principle came from: is there any jewish source to confirm this idea?
Found some comments online that it's a theological (Christian) hermeneutic, but from the sources i quoted it seems to be a 'jewish' thing.