Sharhaan and Fehmaan are not Arabic words. Also such names were not found in the era of the Prophet (may peace and blessings of Allah be upon him) and the Sahabah; hence both these names are not suitable. However, you may keep any name among Aliyan, Abdan and Zakwan. However the best one among them is Zakwan and Abdan. Both have good meaning i.e. ‘sensible and ‘worshipper’. Zakwan had been the name of several Sahabah – may Allah be pleased with them.
Allah knows Best!
Darul Uloom Deoband