What is the Malayalam meaning of English word how did know you?

There isn't a single perfect translation for "How did you know?" in Malayalam that captures all nuances of the English phrase. It depends on the context and intended meaning. Here are some options:

General:

* Nee ethu ariyunnathu engane? (നീ ഇത് അറിയുന്നത് എങ്ങനെ?) - This is a straightforward translation, asking "How did you know this?"

* Ningal engane ariyundu? (നിങ്ങൾ എങ്ങനെ അറിഞ്ഞു?) - This is a more formal way to ask "How did you know?"

Expressing surprise:

* Nee ethu ariyunde? (നീ ഇത് അറിഞ്ഞു?) - This is a surprised question, "Did you know this?"

* Njaan kazhinju engane? (ഞാൻ കഴിഞ്ഞു എങ്ങനെ?) - This is a more informal way to say "How did you know that I knew?"

Expressing curiosity:

* Nee ethu ethra ariyunnu? (നീ ഇത് എത്ര അറിയുന്നു?) - This literally means "How much did you know about this?" but can be used to ask how someone got the information.

The best translation would depend on the context of your question and the intended tone.