The English word climax has two seemingly incompatible meanings of "climax" and "orgasm". Yet, we should not forget that the word has not only a specific meaning, but also a more general, broader meaning, not of a 'specialized' term.
Let's illustrate this via an example: a person may have a profession of a lawyer - yet, within this profession there are many specialties: a judge, an arbitrator, a prosecutor, a notary...
The general meaning for the word climax is 'the highest point, the culmination.' But there are several applied, special, narrower meanings. Climax is the culmination of adulthood - yet, climax as 'orgasm' is the culmination of pleasure.
The etymologist is obliged to grasp a common semantic core, which allows different meanings to co-exist under one 'sound roof'.
I was once amazed that the Arabic word شراء [SHARA] means both “buy” and “sell” at the same time. And now I look at this calmly: both narrow, special meanings go back to the broader, general meaning: "to engage in trade."
Valeriy D. Osipov