imbrication (n.)

"an overlapping of edges" (as of roof tiles, etc.), 1640s, from French imbrication, noun of action from stem of Latin imbricare "to cover with tiles," from imbricem (nominative imbrex) "curved roof tile used to draw off rain," from imber (genitive imbris) "rain, heavy rain; rainwater," from PIE *ombh-ro- "rain" (source also of Sanskrit abhra "cloud, thunder-cloud, rainy weather," Greek ombros "rain, a shower"), from root *nebh- "moist; water" (see nebula).