Understanding the rheological behavior of dilute dispersions of cylindrical nanomaterials in fluids is the first step towards the development of rheological models for these materials. Individual particle tracking was used to quantify the rotational and translational diffusivities of high-aspect-ratio germanium nanowires in alcohol solvents at room temperature. In spite of their long lengths and high aspect ratios, the rods were found to undergo Brownian motion. This work represents the first time that the effects of solvent viscosity and confinement have been directly measured and the results compared to proposed theoretical models. Using viscosity as a single adjustable parameter in the Kirkwood model for Brownian rods was found to be a facile and versatile way of predicting the diffusivities of nanowires across a broad range of length scales.