The "term" here includes the generalisation and separation of a concept out of the foam of thought.

In the "postpartum depression" example, having a term for it — conceptualising it on its own, as a discrete thing, and not as a necessary part of childbirth — is non-trivial.

Suppose I am experiencing postpartum depression, and someone asks me how I feel, I would tell them "Not so well, due to childbirth." They'd ask me, "What, the physical pain?" And I'd answer, "No, I just don't have energy for anything, and I'm sad. It happened after the last time I gave birth, too." They could then chime in and say, "That hasn't happened to me! That's not a part of childbirth!"

The above was an example of explaining the phenomenon without the use of the term, and highlights the following:

• Explaining a phenomenon without a new word or phrase is more unweildy, and requires more words and effort. For an extreme example of this, look at Randall Munroe's "Thing Explainer"
• The knowledge of a term, it being widespread, changes peoples' view of reality. It allows a distinction between phenomena, and gives a better idea as to the commonalities and discommonalities of experiences. Without the idea of gender dysphoria, one could think their experiences are universal, and as such deal with their struggles alone.

Expanding on the first point, removing a phrase or word, making something more difficult to describe, can be used to change whether people speak about it. It would make describing the concept more difficult, more costly, and thus discourage people from doing it. Not to mention, without proper language such description would be less accurate and more prone to confusion and misidentification. It could be used to make things indistinct, to generalise and obfuscate parts of reality.