al-Salāmu ‘alaykum wa rahmatullāh,
In continuing the theme of derivation, a third form was noticed among the linguists, commonly known as al-Ishtiqaaq al-Akbar  (‘The Greatest Derivation’). One angle of this theory is that it went one step further and even claimed, in the presence of certain conditions, there was a link between the common meaning of two triliteral roots that shared only two of the same root letters.
al-Zamakhshari was enthusiastic about this type of ishtiqaaq and tried to derive common meanings for the roots that fell into this category. Some such attempts can be seen scattered through his work on Qur’anic exegesis (tafseer) called al-Kashshaaf. From among his examples are:
The verbs nafaqa نَفَقَ (‘[something] became spent, exhausted’) and nafada نَفَدَ (‘[something] came to an end’, became spent) and nafaa نَفَى (‘he drove [something] away, banished [it]’) are brothers in meaning, the first two root letters of which are noon ن and faa’ ف. Similarly, all other roots beginning with these two letters will indicate a similar meaning related to removal, or deparature.
When the first two root letters are faa’ف and laam ل the meaning indicated is one of breaking something or opening it up. Thus, one says falaqa فَلَقَ to mean ‘he split [a thing]’ (cf: al-Qu’ran, 113:1), falaha فَلَحَ to mean the same thing, falaja فَلَجَ to mean ‘he divided [a thing]’, falaa فَلَى to mean ‘he [dissected the thing until he] examined it in depth’, and so on.
Other examples are that words in which the second root letter is a meen م and the third is a seen س all share the common meaning of secrecy and concealment. Examples of this are namasa نَمَسَ to mean ‘he concealed [a secret]’, tamasa طمس to mean ‘[the path or road or relic etc] became effaced or obliterated’, and ghamasa غَمَسَ to mean ‘he immersed, or sank [something in something else]’.
 The former type was also known as al-Ishtiqaaq al-Akbar by Ibn Jinni, but as al-Ishtiqaaq al-Kabeer by most other linguists.