Almost every attested Songhay variety (Tasawaq is perhaps the only exception) has a reflex of the proto-Songhay word *gúrú "draw water" (from the river, from a pond, from a well, etc.) To express this concept, most Berber varieties (including Tashelhiyt, Kabyle, Tumzabt, Ghadames, Awjila, Tamajeq...) use reflexes of a verb *āgum "draw water", which is thus equally securely reconstructible for proto-Berber. Zenaga, however, has a rather different verb: ägur "puiser l'eau d'un puits, remonter le delou, tirer la corde du seau; faire parvenir qqc (à qqn)" and "se lever (astre)", with an irregular corresponding noun tgäʔrih "eau tirée du puits". It seems to be distinct from äggur "pull".
The only Berber cognates Taine-Cheikh suggests for ägur are reflexes of a verb that may be reconstructed as *agir "throw; rise (of sun)" (eg Tashelhiyt gr, Kabyle gər, Chaoui gər). Presumably the semantic shift of "throw" to "draw water" would be explained via the idea of throwing the bucket down the well. If the comparison is accepted, then the verb shows an innovative semantic shift specific to Zenaga. (It would be interesting to see if Tetserrét shares this, but unfortunately the relevant term doesn't seem to have been recorded.)
If the Zenaga word is indeed cognate to the suggested Berber forms, then it seems reasonable to draw the conclusion that proto-Songhay borrowed *gúrú "draw water" from an early relative of Zenaga. This would fit well with the evidence for a Western Berber language having played an important role in the history of at least northern Mali. If not, then it would become tempting to draw a conclusion much harder to fit with what is known of the region's history: that Zenaga borrowed the word from proto-Songhay.