The "ם" seals off. So אברם is אבר-ם his organ is sealed so he can't be the father of many nations. Only after the Bris and the organ is opened up can he be אב המון גויים. So the "ה" is added to his name which means "הא לכם זרע" - Give them seed [to plant] and he is ready to be אב "ה"מון גויים.
The word גולם [unshaped mass] comes from "גל" reveal and the "ם" seals off any revelation. So a Golem is sealed off from normal human living. See רד"ק in Tehillim [139] - גלמי - הוא הטִפה הקפואה קודם שיציירו בה האיברים , כמו שנקרא העץ 'גולם' טרם שנעשה כלי. "Glum" and "gloomy" are related to גולם.
גדם [a person whose hand is cut off] is גד which means to extend [גוד אחית, גוד אסיק] with a "ם". The extension of his hand is sealed off.
בולם is to stop, seal off. בל means to negate something [בל תוסיף] . The "ם" at the end completely seals it off.
חסום is also a type of sealing off. Many people are emotionally חסומים. They are taking refuge [מחסה] and hiding in there - חסו-ם.
[עי' נוקב מרגלויות פ' ט"ו]
