Why Ponte di Legno is called so?

"Donamus etiam ad prefatum sanctum locum valle illam que vocatur Camonia cum salto Candino vel usque in Dalanias cum montibus at alpibus a fine Treentina qui vocatur Thonale usque in finem Brixamcinse seu giro Bergamasci [...]"

"We also give to the already mentioned holy place [the monastery of Tours] that valley caqlled Camonica, with mountains and passes up until the Dalanias, comprising the mounts and alps bordering with Trentino and the border of Brescia and the lands around Bergamo [...]"

Caroli Magni Diplomata - Papia, XVI Iulius 774


Ponte di Legno, a town built at the confluence of two rivers, crossed by various bridges.
Admit it, you already think to know why it's called so. But you'd be only partially right. While "Ponte" (litt. "bridge") does indeed indicate the presence of a crossing over the river Oglio, "di Legno" (litt. "of wood") has nothing to do with the material used in said bridge, and a lot more with the ancient name of the upper Valley, "Dalania", as indicated by the Carlo Magno donation of 774 d.C. (should you be interested, you may find the link to the latin text of the donation linked at the start of the page, after the quote).
In the course of time Dalania has become "Dalegno"; Ponte was used to indicate the village inside Dalegno where the bridges were (in the same way that "Villa Dalegno" a village nearby, indicated the place where was located the local baptistry.)
Finally, with the translation from the local dialect to Italian during the XIX and XX century, Dalegno became  "di Legno".