Language/wordy names are a human thing, and they are difficult to glean through subconscious means. This is because the subconscious doesn’t use language, it thinks in symbolism and art… the right side, waking mind, conscious brain uses language and has to interpret the symbols into words. It’s possible but you might have to work at it, that interpretation part is tricky.
What I find what works best, is to make up a name for it that you like first. In a calm, quiet state (meditating), reach out in your mind to that feeling of the entity, it’s “energy signature”. This is actually it’s name, but there’s no words for it.
So direct to that entity, “I’m going to call you x, hope that’s ok.” and then you will associate that name you chose with that feeling of who the entity is. It’s like a special shortcut for you that’s easier for you to use as a human.
After that, I think you don’t need a sigil, but you can either make one using the Rose Cross Method, or get one by asking in meditation. You can use the name in meditation and it will very quickly bring up the feeling, then you can direct the question to the entity “please show me what you look like, or your sigil in my minds eye that I can use for sigil work”. Write down what you get back without thinking about it. You conscious mind will want to insert itself, take control and make up answers, it’s just doing it’s job but it’s always wrong so don’t let it.