Proto-Indo-European *derḱ- "to see" became Greek δέρκομαι derkomai "to see clearly", and δράκων drakōn "dragon, serpent" - "from his supposed sharp sight" says Skeat. Δράκων was borrowed into Latin as dracōnem becoming French dragon.
Δράκων was borrowed into Arabic as طرخون ṭarẖwn, a name for tarragon, also known as dragonwort, Latin name Artemisia dracunculus. This was borrowed back into Greek as ταρχών, then into Latin as tarchon, tragonia, then into English as tarragon.
Latin dracōnem became dracunculus, dranculus "small dragon", then Old French drancle, then Anglo-Norman rauncle "festering sore" and rauncler "to fester". The "festering sore" meaning is the earliest meaning of rankle in English.
In Sanskrit *derḱ- became दर्शनं darśanaṃ "seeing, meeting". Darshan refers to a sight or glimpse of a holy personage, such as a guru.