"Original drawings" refers to the first or initial illustrations that are created by an artist. These are the authentic and unique artworks, directly made by the artist themselves, without any copies or reproductions. Full definition
Conversations, observations, and discoveries in the galleries inspire students to create original drawings, paintings, prints, photographs collages, sculptures, and more. (michenerartmuseum.org)
He interacts with the streets by placing these portraits (each an intricate original drawing) back in the environment from where they came. (galleryad.com)
So he decided to create original drawings of pelagic (open ocean) birds and place them in glass bottles along with an information sheet about the project and his contact information. (treehugger.com)