meaning - What does -komu (～込む) at the end of a word mean?

There are loads of words in Japanese which end in 込{こ}む, like 吸{す}い込む, 読{よ}み込む, 入{はい}り込む, 打{う}ち込む, 売{う}り込む, 送{おく}り込む, 押{お}し込む. How does adding ～込む change the meaning? What is the meaning that links all these words?

Answer

込む by itself can be interpreted as a intransitive verb to mean "jammed in", "packed in", "crowded". For example 電車が込む

However, when 込む is used with compound verbs it can have 3 different interpretations.

1. 
   
   

   ‘to enter; put something in/into’

   
   

   Implies a physical transition where an object (or a person) shifts from a place into an enclosed location.

   
   

   Examples
   雨が吹き込む - Rain blows in.
   飛び込む - Jump in/Dive.

   
   


2. 
   

   'to do/become something thoroughly/fully/deeply/intensively'

   
   

   Normally denotes that someone undergoes a certain physical/psychological occurrence that produces physical/mental changes or development.

   
   

   Examples
   
   教え込む - Inculcate a thing (in a person’s mind); instill into (a person); give a good training.
   思い込む - Be convinced; be under the impression; set one’s heart; fall in love.

   
   


3. 
   

   ‘to continue an action within the same condition’

   
   

   Indicates that someone is involved in a physical recurrent action.

   
   

   Examples
   黙り込む - Fall silent; keep one’s mouth shut; clam up.

   
   

Reference: 高橋 直子, “Syntactic Complexity of Komu-compounds in Japanese”, 名古屋外国語大学外国語学部紀要 (Journal of School of Foreign Languages, Nagoya University of Foreign Studies) 36 (2009), 169–193. (PDF)