We wanted to find good rigorous research on this and so we use words based on a research paper by Gaucher, Friesen and Kay (https://pubmed.ncbi.nlm.nih.gov/21381851/).
They looked at the impact of certain words on different genders in the specific context of a job advert. The overall finding was that an increase in masculine wording did cause a decrease in the likelihood of a female candidate applying to a role (the same pattern was found when looking at feminine coded adverts for males but the impact is lessened).
Why, for example, is 'Lead' classed as masculine?
This is actually a question of two parts, which is 'Why do we flag ‘Lead’ in a job advert as masculine' - we do this because, as per the research, that word was found to reduce the likelihood of females applying to the job.
The second question is 'Why is the word 'Lead' perceived as masculine - this is a bigger question. The perception we may have of words being gendered is a result of internalised biases - if for example the majority of times we’ve seen doctors both in real life and in the media, they have been males then we’re more likely to internalise that doctors are mostly men. The same applies to certain phrases and job titles.