風林火山は、孫子(書物)に記された「其疾如風其徐如林侵掠如火不動如山（その疾（はや）きこと風の如く、その徐（しず）かなること林の如く、侵（おか）し掠（かす）めること火の如く、動かざること山の如し）」（孫子ではこの後に「難知如陰　動如雷霆　（知り難きこと陰の如く、動くこと雷霆（らいてい＝雷）の如し）」と続く）という語句を略したものである。

Fu-Rin-Ka-Zan is an abbreviation of the phrase stated in, `Sonshi' (Chinese books about tactics), `其疾如風 其徐如林 侵掠如火 不動如山' (as fast as the wind, as quiet as the forest, as daring as fire, and as immovable as the mountain) (In Sonshi, it is followed by the phrase, `as hard as to understand a shade, as fast as thunder') - Wikipedia日英京都関連文書対訳コーパス

忽敦　「孫子の兵法に『小敵の堅は、大敵の擒なり』とあって『孫子(書物)』謀攻編「故善用兵者、屈人之兵、而非戰也。；拔人之城、而非攻也。；毀人之國、必以全爭于天下、故兵不頓、利可全、此謀攻之法也。故用兵之法、十則圍之、五則攻之、倍則分之、敵則能戰之、少則能守之、不若則能避之。故小敵之堅、大敵之擒也」、少数の兵が力量を顧みずに頑強に戦っても、多数の兵力の前には結局捕虜にしかならないものである。疲弊した兵士を用い、日増しに敵軍が増えている状況で相対させるのは、完璧な策とは言えない。撤退すべきである。」

Dou XIN said, "the Art of War by Tzu SUN tells us that an obstinate attitude leads a small army to being captured by a large army. If the small army fiercely fights against the large army without considering the deference of their fighting strength, it will end up being captured. It is not a perfect plan to force tired soldiers to fight against the enemy that is increasing in number. We should withdraw." - Wikipedia日英京都関連文書対訳コーパス

「疾如風、徐如林、侵掠如火、不動如山」の句は『孫子(書物)』・軍争篇で軍隊の進退について書いた部分にある「其疾如風、其徐如林、侵掠如火、難知如陰、不動如山、動如雷霆。/其の疾きこと風の如く、其の徐（しず）かなること林の如く、侵し掠めること火の如く、知りがたきこと陰の如く、動かざること山の如し、動くこと雷霆（らいてい）の如し」からの引用。

The phrase was quoted from a part written about the attack/withdrawal of an army in the battle section in "Sonshi" (Chinese books about tactics) which says ''as fast as the wind, as quiet as the forest, as daring as fire, as hard to know as dark, as immovable as the mountain, and the movement is like pealing thunder.' - Wikipedia日英京都関連文書対訳コーパス