Multiple global trends and drivers have resulted in a steep escalation of tech-socio-economic inequities in basic human needs across industrialized as well as industrializing nations. This escalation is paralleled by the growing trend of novel and simple frugal innovations for meeting basic human needs, which are applied across various communities in the world towards bridging gaps of inequity. Frugality in this context is defined as minimizing the use of capital resources while delivering effective manufacturing product outcomes. It is noteworthy that frugal innovations are abundantly observed in the biological designs in nature. This paper is aimed at understanding the methodology of frugal engineering behind the resulting frugal manufacturing innovations through discovering the cross-section of frameworks of biological designs in nature and equitable social innovations. Authors have applied the framework of biological designs as these designs are observed to deliver multifunctionality, resilience, and sustainability, which are key to a frugal and equitable innovation platform and achieved by the frugal engineering process. As water is one of the most basic human needs, this paper uses water as an illustrative example to understand the frugal engineering process. The authors discuss designs in nature from cactus, tree roots, and human skin, and design parallels in related frugal innovations namely in fog-capturing nets, ice stupa, and Zeer (pot-in-a-pot), respectively, for equitable water access. The authors propose and discuss a resulting methodology for frugal engineering. This methodology can be utilized as a starting point for developing case-specific socially conscious manufacturing solutions.