Standards and guidelines.

Many guidelines for the design and testing of icons/pictograms/symbols.

On screen icons:
Google Play icon design specifications
TV app icon design guidelines
Design guidelines for Windows app icons
Apple Interface icons. The San Fransisco System font contains thousands of Symbols.
Apple App icons

ISO standards:
ISO 3864-1: 2011. Graphical symbols — Safety colours and safety signs — Part 1: Design principles for safety signs and safety markings.
ISO 3864-3: 2012. Graphical symbols — Safety colours and safety signs - Part 3: Design principles for graphical symbols for use in safety signs.
ISO 7001: 2023. Graphical symbols. Registered public information symbols.
ISO 9186-1: 2014. Graphical symbols. Test methods. Part 1: Method for testing comprehensibility.
ISO 9186-2: 2008. Graphical symbols. Test methods. Part 2: Method for testing perceptual quality.
ISO 9186-3: 2014. Graphical symbols. Test methods. Part 3: Method for testing symbol referent association.
ISO 11469: 2016. Plastics - Generic Identification And Marking Of Plastics Products.
ISO 14026: 2017. Environmental labels and declarations Principles, requirements and guidelines for communication of footprint information.
ISO 14021: 2016. Environmental labels and declarations Self-declared environmental claims (Type II environmental labelling).
ISO 22727: 2007. Graphical symbols. Creation and design of public information symbols. Requirements.
ISO 80416-4: 2005. Basic principles for graphical symbols for use on equipment. Part 4: Guidelines for the adaptation of graphical symbols for use on screens and displays (icons).