As Salaamu a'laykum. We can say جهد is strickly opposed to جهل. The first means "to focus", the second "to be astray". The first carries the etyma JD, a concentration concept, intensity, the second carries the etyma JL to be scattered, like the meaning in Jalaal, the Glory which goes behind limits. So the heart of these 2 words it's the ه infixed, the archetyp of the ideation. Jahal it's to have his thoughts scattered, astray, while in Jahada is to have them concentrated. Because of this perfect consistency, it's true that arabic is mubiyn, and Qiblah of human languages.