Meaning of 'siddham'

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siddham

This ancient word has many meanings in south asian 
languages, evidenced in many epigraphs. 

I shall be grateful for information from scholars on 
cognate words in South Asian and other languages and 
their  guidance on the possible ancient or early 
'meanings' assigned to this word. 

What does siddha-mAtrkA 'mean' when such a name is 
assigned to an ancient script which originated from 
brAhmI and spread to Cambodia and Thailand?

SUCCESS OR READINESS
pra-siddham = famous; What is the etymology for this 
word?
?Perhaps from siddham = success?
e.g. siddhi-r-astu = let there be success.

siddham also connotes 'readiness' when for e.g. the 
armored guard of a king says, 'siddham' or 'I am 
ready (to carry out your orders)'
e.g. saMsiddham in Sanskrit.

PERFECTION
siddhi = (attaining) perfection, e.g. siddha-pITha = 
yoga-pITha a holy place where an ascetic attained 
perfection (siddhi) by his austerities.

PROPERTY RIGHTS
siddhi = income (Tamil); sidd-Ayam = prob. 
agricultural income; a fixed assessment; siddha = 
income from land under cultivation; right of 
cultivating land, one of the eight kinds of rights of 
enjoying  landed property; e.g. 
Urdhv-Adhah-siddhi-yutA = with income from the
produce above and below the surface of the ground or 
together with income from horticulture and 
agriculture; antah-siddhika =  privilege of
the donee of rent-free land (privilege of the donee 
offering full power of adjudication in law-suits); 
siddha-sAdhya  present income and the income that may 
accrue in future.

SCRIPT
siddha-mAtRkA = name of the Indian alphabet derived 
from late brAhmI script which is the source of many 
scripts of south asia; wrongly called kuTila.

siddham is  word that occurs at the beginning of 
inscriptions; is often denoted by a sign at the 
beginning of epigraphic inscriptions perhaps to 
ensure the success of the undertaking? Several 
symbols occur, sometimes the word is denoted by the 
script syllable for CHA. This symbolic representation 
is different from the symbol used for the praNava or 
syllable oM.

SYMBOLS IN brAhmI SCRIPT
The syllable 'cha' is a circle with a vertical line 
dissecting through the middle and protruding on top 
of the circle.

The syllable 'tha' is a circle with a central dot.

SYMBOLS IN TELUGU SCRIPT
In Telugu, the dotted circle denotes 'Tha'; 
in general, a dot inserted connotes an aspirate, e.g. 
'da' becomes 'dha' when a 'dot' is inserted in the 
'leaf or kidney' symbol.