Distributing a modified version of the Rust programming language, compiler, or the Cargo package manager with modifications other than those permitted above and calling it Rust or Cargo requires explicit, written permission from the Rust Foundation.

And Python:

Use of the word "Python" when redistributing the Python programming language as part of a freely distributed application -- Allowed. If the standard version of the Python programming language is modified, this should be clearly indicated. For commercial distributions, contact the PSF for permission if your use is not covered by the nominative use rules described in the section "Uses that Never Require Approval" above.

Let's also look at Perl:

People sometimes ask if TPF's use of an onion in the Perl logo means that independent projects that use or relate to Perl need TPF's permission to use an onion of their own design in connection with their project. ​ The answer is "not necessarily" as long as no likelihood of confusion is created. One of the fundamental legal bases for trademark protection is to make sure that the public can depend on a mark as an accurate indicator of a particular source or relationship, and one way of defining trademark infringement is to say that the infringing mark creates a likelihood of confusion. Likelihood of confusion is determined based not only on making a comparison of the marks side-by-side, but also on making a comparison of the contexts in which they are actually used. Thus, it's easy to imagine independent onions that would be fine, and independent onions that might not be.