Svâbhâvat, Swâbhâvat, or Svâbhâva, according to H.P.B. in her Secret Doctrine may deserve the same type of study that previously done for Fohat. i.e. where does it appears, with what meaning(s), according to “conventional theosophy”.
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According to H.P.B. in her Secret Doctrine :

a) Spelling : 3 different spellings are found

• svâbhâvat : SD – Vol I,pp.3,28,31,46,52,53,60,61,85,98,635, Vol II, p.115
• swâbhâvat : SD – Vol I, pp.83,84,661,
• svâbhâva : SD – Vol I, pp.571

b) What is svâbhâvat/swâbhâvat/svâbhâva :

• the active condition of the one infinite and unknown Essence which exists from all eternity (DS – I. p.3)
• the secondary stage of the Prabhavapyaya (DS – I. p.46)
• the plastic essence that fills the universe, the root of all things (DS – I. p.61)
• the Buddhistic concrete aspect of the abstraction called in Hindu philosophy Mulaprakriti (DS – I. p.61)
• In the Ekasloka-Shastra of Nagarjuna (the Lung-shu of China) called by the Chinese the Yih-shu-lu-kia-lun, it is said that the original word of Yeu is “Being” or “Subhava,” “the Substance giving substance to itself,” also explained by him as meaning ” without action and with action,” “the nature which has no nature of its own.” . Subhava, from which svâbhâvat,is composed of two words: Su “fair,” “handsome,” “good”; Sva, “self”; and bhava, “being” or “states of being.” (DS – I. p.61)
• svâbhâvat is the mystic Essence, the plastic root of physical Nature — “Numbers” when manifested (DS – I. p.98)
• The name is of Buddhist use and a Synonym for the four-fold Anima Mundi (DS – I. p.98)
• Occultists identify it with “FATHER-MOTHER” on the mystic plane (DS – I. p.98)
• the mutable radiance of the Immutable Darkness unconscious in Eternity (DS – I. p.635)

c) What does svâbhâvat do :It emanates the noumenon of matter (DS – I. p.84)

• Gods, Men, Gandharvas, Pisachas, Asuras, Rakshasas, all have been created by svâbhâva (Prakriti, or plastic nature) (DS – I. p.571)
• It passes, at every new rebirth of Kosmos, from an inactive state into one of intense activity; that it differentiates, and then begins its work through that differentiation. This work is KARMA. (DS – I. p.635)
• Everything has come out of Akasa (or svâbhâvat on our earth) in obedience to a law of motion inherent in it (DS – I. p.635)