VenSpec is a spectrometer suite on board ESA's EnVision mission to planet Venus, due for launch in November 2031. VenSpec consists of three spectrometers, VenSpec-M, VenSpec-U and VenSpec-H. VenSpec-H stands for Venus Spectrometer with High resolution. It operates in the near-infrared wavelength range between 1.15 and 2.5 μm and it aims at mapping the near surface atmosphere during the night and the atmosphere above the cloud deck during the day. More specific, VenSpec-H will measure gases related to volcanism and surface changes on Venus. It will perform its measurements by means of nadir observations. In this paper an overview is given of the main design requirements, followed by a description of the design activities performed during the feasibility study (phase A) and the preliminary definition (phase B1) of the instrument, including mathematical modeling and analysis, and prototyping. Focus is put on the optical working principle of the instrument, where an echelle grating, used as diffractive element, is combined with an inventive combination of filters for spectral band selection. The design and development of VenSpec-H is done in a consortium under Belgian management and with important contributions from Belgian, Swiss, Spanish, and Dutch research institutes, universities, and industrial partners.