https://dict.fu-lab.ru/term?tid=1251030

Old French aiglantier, eglenter, eglentier, from aiglant 'wild rosebush' +‎ -ier, with the first element derived from an apparent Vulgar Latin *aquilentum, an irregular derivative of Latin aculeus +‎ -ulentum, possibly a substantivized adjective. The later addition of the suffix -ier is in line with several French names of trees, cf. pommier 'apple-tree', from pomme 'apple' +‎ -ier, or genévrier 'juniper tree', from genièvre +‎ -ier.