Feckless ' spiritless, helpless, futile 'is given in all my desk dictionaries, but only Chambers has feck (nice to see a lost positive found), which comes from effect through vowel-loss and is defined as  efficacy  or  quality. 
( ( ( ( ( ( ( Feckless ' ) ( spiritless ( , ( helpless ( , futile ) ) ) ) ) ( ` ( is ( ( given in ) ( all ( my ( desk dictionaries ) ) ) ) ) ) ) , ) but ) ( ( only Chambers ) ( has ( ( ( feck ( -LRB- ( ( nice ( to ( see ( ( a ( lost positive ) ) found ) ) ) ) -RRB- ) ) ) , ) ( which ( ( ( ( comes ( from effect ) ) ( through vowel-loss ) ) and ) ( is ( defined ( as ( ( efficacy or ) quality ) ) ) ) ) ) ) ) ) ) . )
(ROOT (S (S (NP (NP (NNP Feckless) (POS ')) (NNS spiritless) (, ,) (ADJP (JJ helpless)) (, ,) (NNS futile)) (`` `) (VP (VBZ is) (VP (VBN given) (PRT (RP in)) (NP (PDT all) (PRP$ my) (NN desk) (NNS dictionaries))))) (, ,) (CC but) (S (NP (JJ only) (NNS Chambers)) (VP (VBZ has) (NP (NP (NP (NN feck)) (PRN (-LRB- -LRB-) (NP (JJ nice) (S (VP (TO to) (VP (VB see) (NP (NP (DT a) (VBN lost) (NN positive)) (VP (VBN found))))))) (-RRB- -RRB-))) (, ,) (SBAR (WHNP (WDT which)) (S (VP (VP (VBZ comes) (PP (IN from) (NP (NN effect))) (PP (IN through) (NP (NNS vowel-loss)))) (CC and) (VP (VBZ is) (VP (VBN defined) (PP (IN as) (NP (NN efficacy) (CC or) (NN quality))))))))))) (. .)))
Feck is defined as efficacy or quality.
( Feck ( ( is ( defined ( as ( ( efficacy or ) quality ) ) ) ) . ) )
(ROOT (S (NP (NNP Feck)) (VP (VBZ is) (VP (VBN defined) (PP (IN as) (NP (NN efficacy) (CC or) (NN quality))))) (. .)))